Filtration control is an important property of a drilling fluid, particularly when drilling through permeable formations where the hydrostatic pressure exceeds the formation pressure. It is important for a drilling fluid to quickly form a filter cake which effectively minimizes fluid loss, but which also is thin and erodable enough to allow product to flow into the wellbore during production.
One type of filtration control additive used in water based fluids is water-soluble polymer, typically comprising acrylamide monomer. One disadvantage of water-soluble polymers is that they have limited temperature stability. As wells are drilled deeper, higher bottomhole temperatures are encountered.
Filtration control additives are needed which will quickly form a thin, erodable filter cake, and which have high temperature stability for prolonged periods of time.